Method of informing serving cell of uplink interference at neighbor cell caused by unmanned aerial vehicle

ABSTRACT

A neighboring cell determines that uplink interference from an unmanned aerial vehicle (UAV) exceeds a first threshold at the neighboring cell. The neighboring cell transmits an uplink interference indicator to the UAV. In some examples, the UAV informs its serving cell of the uplink interference experienced by the neighboring cell. The serving cell can utilize information received from the UAV to make handover decisions or scheduling decisions for the UAV that caused the uplink interference. In other examples, the UAV can temporarily refrain from transmitting on at least some of its uplink resources or utilize different uplink resources for uplink data transmissions. In still other examples, the UAV can utilize downlink measurements to select which neighboring base station System Information Block messages should be monitored for an uplink interference indicator.

CLAIM OF PRIORITY

The present application is a continuation of and claims priority to U.S.application Ser. No. 17/718,519, entitled “METHOD OF INFORMING SERVINGCELL OF UPLINK INTERFERENCE AT NEIGHBOR CELL CAUSED BY UNMANNED AERIALVEHICLE” and filed on Apr. 12, 2022; which is a continuation of andclaims priority to U.S. application Ser. No. 16/636,864, entitled“METHOD OF INFORMING SERVING CELL OF UPLINK INTERFERENCE AT NEIGHBORCELL CAUSED BY UNMANNED AERIAL VEHICLE” and filed on Feb. 5, 2020; whichis a national stage application of PCT/US2018/046190, entitled “METHODOF INFORMING SERVING CELL OF UPLINK INTERFERENCE AT NEIGHBOR CELL CAUSEDBY UNMANNED AERIAL VEHICLE” and filed on Aug. 10, 2018; which claimspriority to U.S. Provisional Application No. 62/544,191 filed on Aug.11, 2017; U.S. Provisional Application No. 62/683,381 filed on Jun. 11,2018; and U.S. Provisional Application No. 62/571,976 filed on Oct. 13,2017; all of which are assigned to the assignee hereof and herebyexpressly incorporated by reference in their entirety.

FIELD

This invention generally relates to wireless communications and moreparticularly to mitigating interference caused by unmanned aerialvehicles.

BACKGROUND

Aerial vehicles (AVs), such as drones, have received increasing interestin the past few years. AVs can be used to perform many differentapplications, including package delivery, real-time imaging, videosurveillance, solar farm inspection, fire and storm assessment,search-and-rescue, monitoring of critical infrastructure, and wildlifeconservation. Many of these emerging use cases could benefit fromconnecting the AV to a cellular network as a user equipment (UE) device.

SUMMARY

A neighboring cell determines that uplink interference from an unmannedaerial vehicle (UAV) exceeds a first threshold at the neighboring cell.The neighboring cell transmits an uplink interference indicator to theUAV. In some examples, the UAV informs its serving cell of the uplinkinterference experienced by the neighboring cell. The serving cell canutilize information received from the UAV to make handover decisions orscheduling decisions for the UAV that caused the uplink interference. Inother examples, the UAV can temporarily refrain from transmitting on atleast some of its uplink resources or utilize different uplink resourcesfor uplink data transmissions. In still other examples, the UAV canutilize downlink measurements to select which neighboring base stationSystem Information Block messages should be monitored for an uplinkinterference indicator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system for an example in which uplinkinterference from an unmanned aerial vehicle (UAV) exceeds a firstthreshold at a neighboring cell.

FIG. 2A is a block diagram of an example of the base stations shown inFIG. 1 .

FIG. 2B is a block diagram of an example of the UAV shown in FIG. 1 .

FIG. 3A is a messaging diagram of an example in which a serving cellmakes a handover decision for the UAV in response to the UAV causingexcessive uplink interference at a neighboring cell.

FIG. 3B is a messaging diagram of an example in which a serving cellmakes a scheduling decision for the UAV in response to the UAV causingexcessive uplink interference at a neighboring cell.

FIG. 3C is a messaging diagram of an example in which a UAV stops usinga secondary radio resource in response to causing excessive uplinkinterference at a neighboring cell.

FIG. 3D is a messaging diagram of an example in which a UAV selectswhich System Information Block (SIB) messages to monitor based on thesignal strength of downlink signals received at the UAV from theneighboring cells.

FIG. 4A is a flowchart of an example of a method in which a serving cellmakes a handover decision for the UAV in response to the UAV causingexcessive uplink interference at a neighboring cell.

FIG. 4B is a flowchart of an example of a method in which a serving cellmakes a scheduling decision for the UAV in response to the UAV causingexcessive uplink interference at a neighboring cell.

FIG. 4C is a flowchart of an example of a method in which a UAV stopsusing a secondary radio resource in response to causing excessive uplinkinterference at a neighboring cell.

FIG. 4D is a flowchart of an example of a method in which a UAV selectswhich System Information Block (SIB) messages to monitor based on thesignal strength of downlink signals received at the UAV from theneighboring cells.

DETAILED DESCRIPTION

There are a number of important considerations when connecting anunmanned aerial vehicle (UAV) to a network as a user equipment (UE)device. One example of a network to which the UAV can be connected is a3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE)network. In other examples, the network is a fifth generation wirelesssystem (5G) New Radio network. Regardless of the particular network towhich the UAV connects, enhancements may be identified to better preparethe cellular networks for the data traffic growth from UAVs, such asdrones, in the coming years.

When the UAV is flying well above a base station (eNB) antenna height,the uplink signal, which is transmitted from the UAV, may be received bymultiple cells (e.g., base stations) due to line-of-sight propagationconditions. Thus, the likelihood of the uplink signal from the UAVcausing interference to neighboring cells increases as the altitude ofthe UAV increases. In the scenarios in which the uplink signals from theUAV are considered to be interference to one or more neighboring cells,the interference gives a negative impact to the UE devices on the ground(e.g., smartphones, Internet of Things (IoT) devices, etc.).

To prevent such uplink interference, one or more cells that are notproviding services to the UAV may vary their antenna beam patterns tosteer away from the interfering UAV. In addition, the cell that isproviding services to the UAV (e.g., serving cell or serving basestation) may steer its antenna beam pattern towards the UAV. However,such antenna steering mechanisms are complicated and may impact servicesto terrestrial UE devices.

Due to uplink interference experienced by neighboring cells, it isimportant that the UAV's serving cell accounts for such interferenceduring handovers. For example, the serving cell could handover the UAVto a neighboring cell that has the smallest uplink pathloss so that theUAV's transmit power may be minimized, which will also minimize uplinkinterference to neighboring cells. In other cases, the UAV's servingcell may try to allocate uplink resources not used by neighboring cellsto avoid uplink interference.

However, in both cases, tight network coordination is needed, which maynot be readily available today or in the foreseeable future. In somecases, network coordination may not even be possible due to the lack ofbackhaul link among cells (e.g., no X2 links), but without neighbor cellinformation, it is difficult for the serving cell to optimize thehandover or allocate orthogonal resources to the UAV.

Based on the above observations, there is a need for the serving cell tobe informed of the neighbor cells' uplink interference condition withouttight network coordination. Some of the examples described hereininclude a method and a system for informing the serving cell of theneighbor cells' uplink interference condition via the UAV to solve theabove problems. In other examples, the UAV takes action to mitigateinterference at the neighboring cells without involving the servingcell.

FIG. 1 is a block diagram of a communication system for an example inwhich uplink interference from an unmanned aerial vehicle (UAV) exceedsa first threshold at a neighboring cell. The communication system 100 ispart of a radio access network (not shown) that provides variouswireless services to UE devices that are located within the respectiveservice areas of the various base stations that are part of the radioaccess network. Base station 102 is connected to the network through abackhaul (not shown) in accordance with known techniques. The basestation 102 provides wireless services to UAV 106, which functions as aUE device in the examples herein. The base station 102 communicates withUAV 106 via communication link 104.

Although the UAV 106 is located above service area 103 of the basestation 102 in FIG. 1 , base station 102, in this example, is theserving base station for the UAV 106. For example, although the serviceareas 103, 110, 116 are shown as two-dimensional areas in FIG. 1 , it isunderstood that for purposes of providing services to a UAV, the serviceareas actually extend upwards vertically to provide services to UAVsthat may be located at various altitudes above the service areas shownin FIG. 1 . Specifically, the determination of which base station isused to serve the UAV 106 in the Connected mode is controlled by thenetwork according to multiple factors such as loading of the neighboringbase stations, the base station antenna configurations, and the downlinksignal strength measurements reports from the UAV 106. In this regard,it is worth noting that, similar to the coverage area that can beprovided to traditional, terrestrial UE devices by a base station, thecoverage area that can be provided to a UAV by a base station can alsobe affected by distance, environmental conditions, obstructions, andinterference.

In the example shown in FIG. 1 , communication link 104 is a Uu linkbetween the UAV 106 and the base station (eNB) 102. Communication link104 is configured to provide downlink communication from the basestation 102 to the UAV 106 and to provide uplink communication from theUAV 106 to the base station 102.

In the interest of clarity and brevity, communication system 100 isshown as having only two neighboring base stations 108, 114, whichprovide wireless services to UE devices located within their respectiveservice areas 110, 116. However, in other examples, communication system100 could have any suitable number of base stations. In the exampleshown in FIG. 1 , base station 102 is considered to be a serving basestation since it is providing wireless services to UAV 106. However,neighboring base stations 108, 114 are also capable of providingwireless services to the UAV 106 via their respective communicationlinks 112, 118, if the UAV 106 is handed over to one of the neighboringbase stations 108, 114. Communication links 112, 118 are similar tocommunication link 104. If, for example, the UAV 106 is handed over toneighboring base station 108, then neighboring base station 108 wouldbecome the serving base station, and base station 102 would become aneighboring base station. For the purposes of the examples describedherein, base stations are considered to be neighboring each other ifthey are relatively close to each other and/or the UAV 106 cansimultaneously receive signals from each of the neighboring basestations at a given time.

Base station 102, which is sometimes referred to as an eNodeB or eNB,communicates with the UAV 106 by transmitting downlink signals viacommunication link 104. In the case of 5G based on New Radio, the basestation is sometimes referred to as a gNB. Base station 102 alsoreceives uplink signals transmitted from the UAV 106 via communicationlink 104. As used herein, the terms “base station” and “cell” areinterchangeable. In some cases, the serving cell is provided by a firstbase station, and the neighboring cell is provided by a second basestation. However, in other cases, a serving cell and a neighboring cellmay be provided by the same base station.

Although FIG. 2A specifically depicts the circuitry and configuration ofserving base station 102, the same base station circuitry andconfiguration that is shown and described in connection with servingbase station 102 is also utilized for neighboring base stations 108, 114in the example shown in FIG. 1 . In other examples, either of the basestations may have circuitry and/or a configuration that differs fromthat of the serving base station 102 shown in FIG. 2A.

As shown in FIG. 2A, base station 102 comprises controller 204,transmitter 206, and receiver 208, as well as other electronics,hardware, and code. The base station 102 is any fixed, mobile, orportable equipment that performs the functions described herein. Thevarious functions and operations of the blocks described with referenceto the base station 102 may be implemented in any number of devices,circuits, or elements. Two or more of the functional blocks may beintegrated in a single device, and the functions described as performedin any single device may be implemented over several devices.

For the example shown in FIG. 2A, the base station 102 may be a fixeddevice or apparatus that is installed at a particular location at thetime of system deployment. Examples of such equipment include fixed basestations or fixed transceiver stations. In some situations, the basestation 102 may be mobile equipment that is temporarily installed at aparticular location. Some examples of such equipment include mobiletransceiver stations that may include power generating equipment such aselectric generators, solar panels, and/or batteries. Larger and heavierversions of such equipment may be transported by trailer. In still othersituations, the base station 102 may be a portable device that is notfixed to any particular location. Accordingly, the base station 102 maybe a portable user device such as a UE device in some circumstances.

The controller 204 includes any combination of hardware, software,and/or firmware for executing the functions described herein as well asfacilitating the overall functionality of the base station 102. Anexample of a suitable controller 204 includes code running on amicroprocessor or processor arrangement connected to memory. Thetransmitter 206 includes electronics configured to transmit wirelesssignals. In some situations, the transmitter 206 may include multipletransmitters. The receiver 208 includes electronics configured toreceive wireless signals. In some situations, the receiver 208 mayinclude multiple receivers. The receiver 208 and transmitter 206 receiveand transmit signals, respectively, through an antenna 210. The antenna210 may include separate transmit and receive antennas. In somecircumstances, the antenna 210 may include multiple transmit and receiveantennas.

The transmitter 206 and receiver 208 in the example of FIG. 2A performradio frequency (RF) processing including modulation and demodulation.The receiver 208, therefore, may include components such as low noiseamplifiers (LNAs) and filters. The transmitter 206 may include filtersand amplifiers. Other components may include isolators, matchingcircuits, and other RF components. These components in combination orcooperation with other components perform the base station functions.The required components may depend on the particular functionalityrequired by the base station.

The transmitter 206 includes a modulator (not shown), and the receiver208 includes a demodulator (not shown). The modulator modulates thedownlink signals to be transmitted via communication link 104 and, in sodoing, can apply any one of a plurality of modulation orders. Thedemodulator demodulates any uplink signals received at the base station102 in accordance with one of a plurality of modulation orders.

Returning to FIG. 1 , the communication system 100 provides variouswireless services to the UAV 106 via base station 102. For the exampleshown in FIG. 1 , the communication system 100 operates in accordancewith at least one revision of the 3rd Generation Partnership Project(3GPP) communication specification. In the example shown in FIG. 2B, theUAV 106 circuitry is configured to communicate directly with the basestation 102. For example, the UAV 106 receives downlink signals viacommunication link 104 using antenna 212 and receiver 214. The UAV 106transmits uplink signals using transmitter 218 and antenna 212.

Besides antenna 212 and receiver 214, the UAV 106 further comprisescontroller 216 and transmitter 218, as well as other electronics,hardware, and code. The UAV 106 is any fixed, mobile, or portableequipment that performs the functions described herein. The variousfunctions and operations of the blocks described with reference to theUAV 106 may be implemented in any number of devices, circuits, orelements. Two or more of the functional blocks may be integrated in asingle device, and the functions described as performed in any singledevice may be implemented over several devices.

For the examples described herein, the UAV 106 is any wirelesscommunication device that is capable of flight without having a humanpilot aboard. In some examples, UAV 106 may be connected to an EvolvedUniversal Mobile Telecommunications System Terrestrial Radio AccessNetwork (E-UTRAN) when flying and when on the ground. A drone would beone example of UAV 106. In the instances where the UAV 106 is a drone,the flight of the UAV 106 may operate with various degrees of autonomy,either under remote control by a human operator, autonomously by anonboard computer, or autonomously by a remote computer. In other cases,the UAV 106 may be a kite whose height can be manually adjusted by ahuman operator. In still other cases, the UAV 106 may be a kite whoseheight can be adjusted by an adjustable mechanized tether, which can becontrolled by a human operator, by a programmed algorithm, or by the UAV106 itself.

The controller 216 of the UAV 106 includes any combination of hardware,software, and/or firmware for executing the functions described hereinas well as facilitating the overall functionality of a UE device. Anexample of a suitable controller 216 includes code running on amicroprocessor or processor arrangement connected to memory. Thetransmitter 218 includes electronics configured to transmit wirelesssignals. In some situations, the transmitter 218 may include multipletransmitters. The receiver 214 includes electronics configured toreceive wireless signals. In some situations, the receiver 214 mayinclude multiple receivers. The receiver 214 and transmitter 218 receiveand transmit signals, respectively, through antenna 212. The antenna 212may include separate transmit and receive antennas. In somecircumstances, the antenna 212 may include multiple transmit and receiveantennas.

The transmitter 218 and receiver 214 in the example of FIG. 2B performradio frequency (RF) processing including modulation and demodulation.The receiver 214, therefore, may include components such as low noiseamplifiers (LNAs) and filters. The transmitter 218 may include filtersand amplifiers. Other components may include isolators, matchingcircuits, and other RF components. These components in combination orcooperation with other components perform the UE device functions. Therequired components may depend on the particular functionality requiredby the UE device (e.g., UAV 106).

The transmitter 218 includes a modulator (not shown), and the receiver214 includes a demodulator (not shown). The modulator can apply any oneof a plurality of modulation orders to modulate signals prior totransmission. The demodulator demodulates received signals in accordancewith one of a plurality of modulation orders.

In operation, serving base station 102 provides wireless services to(e.g., serves) UAV 106 via communication link 104. However, due to thealtitude at which the UAV 106 operates, the uplink transmissions fromthe UAV 106 may cause interference with one or more neighboring basestations 108, 114. More specifically, the uplink data transmissions fromUAV 106 may interfere with the uplink data transmissions beingtransmitted by UE devices (not shown in FIG. 1 ) located within therespective service areas 110, 116 of the neighboring base stations 108,114. As mentioned above, some of the examples described herein include amethod and a system for informing the serving cell 102 of the neighborcells' uplink interference condition via the UAV 106 to solveinterference problems caused by the UAV 106. In other examples, the UAV106 takes action to mitigate interference at the neighboring cells 108,114 without involving the serving cell 102.

FIGS. 3A-3D depict the signals that are transmitted between the UAV 106,the serving base station 102, and a neighboring base station 108,according to several different examples in which the UAV 106 is informedof the uplink interference condition of neighboring base station 108. Inthe interest of clarity and brevity, not all of the messages that aretransmitted between the UAV 106 and the base stations 102, 108 areincluded in FIGS. 3A-3D. Moreover, one or more of the messages that areshown in FIGS. 3A-3D may be omitted. Likewise, additional messages maybe included beyond those shown in FIGS. 3A-3D that facilitate themitigation of uplink interference experienced by the neighboring basestation 108. Furthermore, the various signals shown in FIGS. 3A-3D maybe combined with each other and/or substituted in any suitable mannerthat facilitates the mitigation of uplink interference experienced bythe neighboring base station 108.

FIG. 3A is a messaging diagram of an example in which a serving cell 102makes a handover decision for the UAV 106 in response to the UAV 106causing excessive uplink interference at a neighboring cell 108. Thehandover decision for UAV 106 may have a profound impact on the severityof uplink interference due to the differences in the transmit power ofthe UAV 106 towards the selected target cell 108 for handover. In orderfor the serving cell 102 to make the proper handover decision, theserving cell 102 needs to know the extent of the uplink interferencetowards the neighboring cell(s) 108, 114. In some cases, the neighboringcell 108 that experiences the worst uplink interference may be the besttarget cell for handover. FIG. 3A depicts the messages that areexchanged between the UAV 106 and the base stations 102, 108 to make aninformed handover decision.

In the example shown in FIG. 3A, the UAV 106 transmits, via transmitter218 and antenna 212, uplink transmissions that are intended for theserving cell (e.g., base station) 102. However, these uplinktransmissions create unintended interference at neighboring cell (e.g.,base station) 108. The base stations 102, 108 receive the uplinktransmissions via their respective antennas 210 and receivers 208. Thesignal containing the uplink transmissions is represented in FIG. 3A bysignal 302. In other examples, UAV 106 may transmit a Sounding ReferenceSignal (SRS) or a signal on the Physical Random Access Channel (PRACH)for uplink detection at the neighboring base station 108. The SRS andthe PRACH signal can be configured by the serving cell 102.

Upon receipt of the uplink transmissions 302 from the UAV 106, thecontroller 204 of neighboring base station 108 determines whether theuplink transmissions 302 received from the UAV 106 are causing a levelof interference at the neighboring cell 108 that exceeds an interferencethreshold. If the interference caused by the uplink transmissions 302exceeds the interference threshold, the neighboring base station 108transmits, via its transmitter 206 and antenna 210, an uplinkinterference indicator to the UAV 106. The UAV 106 receives the uplinkinterference indicator with antenna 212 and receiver 214. The signalcontaining the uplink interference indicator is represented in FIG. 3Aby signal 304.

In some cases, the neighboring cell 108 transmits the uplinkinterference indicator to the UAV 106 over a Multicast-Broadcast SingleFrequency Network (MBSFN) channel. In other cases, the neighboring cell108 transmits the uplink interference indicator to the UAV 106 over aSystem Information Block (SIB).

In some examples, the uplink interference indicator includes anidentifier of the neighboring cell 108. For example, the identifier ofthe neighboring cell 108 may be a Physical Cell Identifier (PCI)associated with the neighboring cell 108. In other examples, the uplinkinterference indicator comprises a location of uplink radio resourceswhere the uplink interference occurred.

In still other examples, the uplink interference indicator comprises amultiple threshold indicator comprising one or more bits. For example,if the neighboring cell 108 is configured to compare the uplinkinterference with multiple interference thresholds, each of which isindicative of a different level of uplink interference being experiencedby the neighboring cell 108, the uplink interference indicator could beset to reflect one of the multiple thresholds that is representative ofthe level of uplink interference being experienced by the neighboringcell 108. More specifically, a 1-bit uplink interference indicator couldbe used to represent 2 different interference thresholds, and a 2-bituplink interference indicator could be used to represent 4 differentinterference thresholds.

Upon receipt of the uplink interference indicator, the controller 216 ofthe UAV 106 determines that the uplink interference indicator isaddressed to the UAV 106 based on the timing of the uplink transmissionsfrom the UAV 106 and the timing of the reception of the uplinkinterference indicator. However, in other examples, identifiers for anyUAVs operating in the area may be shared among nearby cells so that theneighboring cell 108 can identify the interfering UAV 106. Thus, inthese examples, the uplink interference indicator may also include anidentifier associated with the interfering UAV 106.

Upon determining that the uplink interference indicator is addressed tothe UAV 106, the UAV 106 informs the serving cell 102 of the uplinkinterference experienced by the neighboring cell 108. For the exampleshown in FIG. 3A, the UAV 106 transmits, via transmitter 218 and antenna212, a message, including the neighboring cell identifier, which wasreceived with the uplink interference indicator, to the serving cell 102to inform the serving cell 102 of the uplink interference experienced byneighboring cell 108. In some examples in which more than oneneighboring cell 108, 114 is experiencing excessive uplink interferencefrom the UAV 106, the UAV 106 only informs the serving cell 102 of theneighboring cell 108 with the worst uplink interference, as reflected bythe multiple threshold interference indicators discussed above. Theserving cell 102 receives, via its antenna 210 and receiver 208, theidentifier of the neighboring cell 108. The signal containing theneighboring cell identifier is represented in FIG. 3A by signal 306. Inother examples, the UAV 106 may inform the serving cell 102 of all orsome of the neighboring cells 108, 114 that indicated that they wereexperiencing excessive uplink interference.

In some examples, the UAV 106 transmits, via transmitter 218 and antenna212, the uplink interference indicator, along with or separate from theneighboring cell identifier, to the serving cell 102 to inform theserving cell 102 of the uplink interference experienced by theneighboring cell 108. The serving cell 102 receives, via its antenna 210and receiver 208, the uplink interference indicator. Receipt of theuplink interference indicator triggers the serving cell 102 to transmit,via its transmitter 206 and antenna 210, the uplink interferenceindicator in a System Information Block (SIB) message. By broadcastingthe uplink interference indicator, which pertains to neighboring cell108, in the serving cell 102, other UAVs will not need to monitor theSystem Information of the neighboring cell 108 to read the SIB messagingin order to find out if the neighboring cell 108 is broadcasting anuplink interference indicator. This broadcasting of the uplinkinterference indicator of the neighboring cell 108 by the serving cell102 efficiently informs nearby UAVs whether the neighboring cell 108 isbroadcasting an uplink interference indicator.

In other examples, the receiver 214 of the UAV 106 is configured tomonitor System Information Block (SIB) messaging from the neighboringcell 108, in response to the controller 216 of the UAV 106 determiningthat a signal strength of a downlink signal received at the UAV 106 fromthe neighboring cell 108 exceeds a downlink signal strength threshold.For example, the UAV 106 could choose to read the SIB messages from onlythose neighboring base stations that have a downlink signal strength(e.g., Reference Signals Received Power (RSRP)) greater than a certainsignal strength threshold measured at the UAV 106. This signal strengththreshold could be defined by the network. In Frequency Division Duplex(FDD) deployments, the UAV 106 could assume that a neighboring basestation 108 is receiving the uplink signal from the UAV 106 at astrength that is similar to the strength at which the UAV 106 isreceiving the downlink signal from the same neighboring base station108. In a Time Division Duplex (TDD) deployment, a simpledownlink-uplink reciprocity is applied to determine the strength atwhich signals are being received between the UAV 106 and the neighboringbase station 108.

Receipt of the uplink interference indicator also triggers thecontroller 216 of the UAV 106 to generate a downlink measurement reportassociated with downlink transmissions received by the UAV 106 from theneighboring cell 108 that sent the uplink interference indicator signal304. In some examples, the UAV 106 generates a downlink measurementreport that pertains to the uplink interference indicator signal 304received from the neighboring cell 108, which may or may not have thehighest downlink signal strength in a list of neighboring cells 108,114. In other examples, the neighboring cell identifier is included withthe downlink measurement report, if the neighboring cell identifier wasnot included in signal 306. The UAV 106 transmits, via transmitter 218and antenna 212, the downlink measurement report to the serving cell102. The serving cell 102 receives, via its antenna 210 and receiver208, the downlink measurement report. The signal containing the downlinkmeasurement report is represented in FIG. 3A by signal 308.

Upon receipt of the downlink measurement report, the controller 204 ofthe serving cell 102 determines whether UAV 106 should be handed over toneighboring cell 108 based on the contents of the uplink interferenceindicator (e.g., the neighboring cell identifier associated with theneighboring cell 108 that experienced the uplink interference) and thedownlink measurement report associated with neighboring cell 108. Insome examples, the serving cell 102 may also request an uplinkmeasurement report from the neighboring cell 108 regarding the uplinksignal strength associated with the UAV 106. The request for the uplinkmeasurement report and the corresponding response are transmitted via awired connection (e.g., X2) between the serving cell 102 and theneighboring cell 108 and are represented in FIG. 3A by signal 310.

If the UAV 106 should be handed over, the serving cell 102 transmits,via its transmitter 206 and antenna 210, a handover command to informthe UAV 106 to handover to the neighboring cell 108. The UAV 106receives the handover command with antenna 212 and receiver 214. Thesignal containing the handover command is represented in FIG. 3A bysignal 312.

Upon receipt of the handover command, the UAV 106 complies with thehandover command to perform a handover procedure to neighboring cell108. In order to complete the handover procedure, the UAV 106 transmits,via transmitter 218 and antenna 212, a Radio Resource Control (RRC)Connection Reconfiguration Complete message to the neighboring cell 108.The neighboring cell 108 receives the RRC Connection ReconfigurationComplete message with its antenna 210 and receiver 208. The signalcontaining the RRC Connection Reconfiguration Complete message isrepresented in FIG. 3A by signal 314. Once the handover procedure iscomplete, the neighboring cell 108 becomes the serving cell for the UAV106, and the serving cell 102 becomes a neighboring cell for the UAV106.

FIG. 3B is a messaging diagram of an example in which a serving cell 102makes a scheduling decision for the UAV 106 in response to the UAV 106causing excessive uplink interference at a neighboring cell 108. Besidesusing the uplink interference indicator to make handover decisions asshown above in connection with FIG. 3A, the uplink interferenceindicator may also be used for making scheduling decisions. For example,when a neighboring cell 108 experiences excessive uplink interferencefrom the UAV 106, the neighboring cell 108 sends the uplink interferenceindicator to the UAV 106. The neighboring cell 108 may also include thelocation of the uplink radio resources where the interference occurred.When the UAV 106 receives the uplink interference indicator, the UAV 106informs its serving cell 102 of this uplink interference, and theserving cell 102 has the option to reconfigure a different uplink radioresource to the UAV 106. FIG. 3B depicts the messages that are exchangedbetween the UAV 106 and the base stations 102, 108 so that the servingcell 102 can make an informed scheduling decision.

Initially, the UAV 106 transmits, via transmitter 218 and antenna 212,uplink transmissions that are intended for the serving cell (e.g., basestation) 102. However, these uplink transmissions create unintendedinterference at neighboring cell (e.g., base station) 108. The basestations 102, 108 receive the uplink transmissions via their respectiveantennas 210 and receivers 208. The signal containing the uplinktransmissions is represented in FIG. 3B by signal 302.

Upon receipt of the uplink transmissions 302 from the UAV 106, thecontroller 204 of neighboring base station 108 determines whether theuplink transmissions 302 received from the UAV 106 are causing a levelof interference at the neighboring cell 108 that exceeds an interferencethreshold. If the interference caused by the uplink transmissions 302exceeds the interference threshold, the neighboring base station 108transmits, via its transmitter 206 and antenna 210, an uplinkinterference indicator to the UAV 106. The UAV 106 receives the uplinkinterference indicator with antenna 212 and receiver 214. The signalcontaining the uplink interference indicator is represented in FIG. 3Bby signal 304.

In some cases, the neighboring cell 108 transmits the uplinkinterference indicator to the UAV 106 over a Multicast-Broadcast SingleFrequency Network (MBSFN) channel. In other cases, the neighboring cell108 transmits the uplink interference indicator to the UAV 106 over aSystem Information Block (SIB). In other examples, the uplinkinterference indicator also comprises a location of uplink radioresources where the uplink interference occurred.

In some examples, the uplink interference indicator comprises a singlethreshold indicator comprising one bit. For example, if the neighboringcell 108 is configured to compare the uplink interference with a singleinterference threshold, the uplink interference indicator could be setto indicate whether the level of uplink interference being experiencedby the neighboring cell 108 is above or below the interferencethreshold.

Upon receipt of the uplink interference indicator, the UAV 106 informsthe serving cell 102 of the uplink interference problem. For the exampleshown in FIG. 3B, the UAV 106 transmits, via transmitter 218 and antenna212, a feedback indicator to the serving cell 102 to inform the servingcell 102 of the uplink interference problem. The serving cell 102receives, via its antenna 210 and receiver 208, the feedback indicator.The signal containing the feedback indicator is represented in FIG. 3Bby signal 318.

In response to receiving the feedback indicator, the controller 204 ofthe serving cell 102 determines that the UAV 106 should be configuredwith a new uplink radio resource. The new uplink radio resource shouldbe an allocation of an uplink radio resource that is different than theuplink radio resource that was utilized when the UAV 106 caused theuplink interference that triggered transmission of the uplinkinterference indicator and, subsequently, the feedback indicator.

The serving cell 102 transmits, via its transmitter 206 and antenna 210,a new uplink grant to the UAV 106. The new uplink grant specifies thenew (e.g., different) uplink radio resource that should be used by theUAV 106. The UAV 106 receives the new uplink grant with antenna 212 andreceiver 214. The signal containing the new uplink grant is representedin FIG. 3B by signal 320.

Upon receipt of the new uplink grant, the UAV 106 resumes its uplinktransmissions, utilizing the new uplink radio resource specified in thenew uplink grant. The UAV 106 transmits, via transmitter 218 and antenna212, uplink transmissions to the serving cell 102. The serving cell 102receives the uplink transmissions with its antenna 210 and receiver 208.The signals containing the uplink transmissions are represented in FIG.3B by signal 322.

FIG. 3C is a messaging diagram of an example in which a UAV 106 stopsusing a secondary radio resource in response to causing excessive uplinkinterference at a neighboring cell 108. Besides the handover decisionand the scheduling decision described above, the uplink interferenceindicator may also be used for making decisions regarding the use of asecondary resource in a dual connectivity or carrier aggregationscenario. For such a scenario, it is assumed that two uplink radioresources are available (e.g., a primary radio resource and a secondaryradio resource) for use by the UAV 106.

The primary radio resource will be a dedicated resource for the UAV 106that does not interfere with the uplink transmissions of neighboringcells 108, 114. In some cases, the primary uplink radio resource is adedicated frequency channel, and in other cases, the primary radioresource is a Time Division Duplex (TDD) resource orthogonal to uplinkresources used by neighboring cells 108, 114. Typically, the command andcontrol of the UAV 106 will utilize the primary radio resource since thecontrol of the UAV 106 should not be compromised. The command andcontrol of the UAV 106 does not usually require a large amount of uplinkresource. Thus, a narrowband channel will be sufficient forcommunications associated with the command and control of the UAV 106.

However, uplink video transmissions from the UAV 106 will utilize thesecondary radio resource. Unlike the primary radio resource, the uplinktransmissions from the UAV 106 on the secondary radio resource mayinterfere with the neighboring cells 108, 114. In order to support thetransmission of video from the UAV 106, the secondary radio resourcetypically has a much larger bandwidth pipe than the primary radioresource.

When the neighboring cell 108 experiences excessive uplink interferenceon the secondary radio resource, the neighboring cell 108 will send anuplink interference indicator to the UAV 106. After receiving the uplinkinterference indicator, the UAV 106 will temporarily stop using thesecondary radio resource and stop the video transmissions. In someexamples, the secondary radio resource may be allocated fordevice-to-device (D2D) communication whereby multiple UE devices and/orUAVs may use the same resource. In other examples, the UAV 106 may beconfigured to incorporate energy-detection or listen-before-talk on thesecondary radio resource to reduce the likelihood of collision amongtransmissions from other UAVs using the same resource. FIG. 3C depictsthe messages that are exchanged between the UAV 106 and the basestations 102, 108 so that the UAV 106 can make an informed decisionregarding the use of a secondary resource in a dual connectivity orcarrier aggregation scenario.

The serving cell 102 transmits, via its transmitter 206 and antenna 210,an uplink resource configuration to the UAV 106. The uplink resourceconfiguration specifies the primary and secondary radio resources thatshould be used by the UAV 106. The UAV 106 receives the uplink resourceconfiguration with antenna 212 and receiver 214. The signal containingthe uplink resource configuration is represented in FIG. 3C by signal324.

The UAV 106 transmits uplink data using the configured primary andsecondary radio resources. For example, the UAV 106 transmits, viatransmitter 218 and antenna 212, the video as an uplink transmissionthat is intended for the serving cell (e.g., base station) 102. However,at least some of these uplink transmissions create unintendedinterference at neighboring cell (e.g., base station) 108. The basestations 102, 108 receive the uplink transmissions via their respectiveantennas 210 and receivers 208. The signal containing the uplinktransmissions is represented in FIG. 3C by signal 326.

Upon receipt of the uplink transmissions 326 from the UAV 106, thecontroller 204 of neighboring base station 108 determines whether theuplink transmissions 326 received from the UAV 106 are causing a levelof interference at the neighboring cell 108 that exceeds an interferencethreshold. If the interference caused by the uplink transmissions 326exceeds the interference threshold, the neighboring base station 108transmits, via its transmitter 206 and antenna 210, an uplinkinterference indicator to the UAV 106. The UAV 106 receives the uplinkinterference indicator with antenna 212 and receiver 214. The signalcontaining the uplink interference indicator is represented in FIG. 3Cby signal 304.

In some examples, the uplink interference indicator comprises a singlethreshold indicator comprising one bit. For example, if the neighboringcell 108 is configured to compare the uplink interference with a singleinterference threshold, the uplink interference indicator could be setto indicate whether the level of uplink interference being experiencedby the neighboring cell 108 is above or below the interferencethreshold. In other examples, the uplink interference indicator alsocomprises a time window to facilitate determination of which UAV 106caused the uplink interference at the neighboring cell 108. In stillother examples, the uplink interference indicator also comprises alocation of uplink radio resources where the uplink interferenceoccurred.

Upon receipt of the uplink interference indicator, the UAV 106 refrainsfrom transmitting on at least a portion of the uplink radio resourcesthat have been assigned to the UAV 106 for uplink transmissions. In someexamples, the UAV 106 temporarily stops transmitting video on thesecondary radio resource. For examples in which the uplink interferenceoccurs within a shared secondary radio resource, the UAV 106 temporarilystops transmitting video on the shared secondary radio resource.

After a period of time, the UAV 106 resumes transmission on the uplinkradio resources. In some cases, the period of time is based onexpiration of a timer. Before resuming transmission on the uplink radioresources, the UAV 106 has the option of selecting a different subset ofthe secondary uplink radio resource to use when transmitting is resumed.

The UAV 106 resumes its uplink transmissions, via transmitter 218 andantenna 212, to the serving cell 102. The serving cell 102 receives theuplink transmissions with its antenna 210 and receiver 208. The signalscontaining the uplink transmissions are represented in FIG. 3C by signal328.

FIG. 3D is a messaging diagram of an example in which a UAV 106 selectswhich System Information Block (SIB) messages to monitor based on thesignal strength of downlink signals received at the UAV 106 from theneighboring cells 108, 114. As mentioned above, the neighboring cell 108can send the uplink interference indicator using an SIB message.However, in order to receive the uplink interference indicator, the UAV106 has to monitor a large number of SIB messages transmitted by theneighboring cells 108, 114. The UAV 106 does not know beforehand whethera particular neighboring cell is the victim of interference caused byuplink transmissions from the UAV 106. Monitoring a large number ofdownlink SIB messages is very inefficient as it takes a large amount oftime for the UAV 106 to read each SIB message, which leads to additionalcomplexities and higher power consumption.

In order to down-select to a smaller number of SIB messages, the UAV 106could choose to read the SIB messages from only those neighboring basestations that have a downlink signal strength (e.g., Reference SignalsReceived Power (RSRP)) greater than a certain signal strength thresholdmeasured at the UAV 106. This signal strength threshold could be definedby the network. In Frequency Division Duplex (FDD) deployments, the UAV106 could assume that a neighboring base station 108 is receiving theuplink signal from the UAV 106 at a strength that is similar to thestrength at which the UAV 106 is receiving the downlink signal from thesame neighboring base station 108. In a TDD deployment, a simpledownlink-uplink reciprocity is applied to determine the strength atwhich signals are being received between the UAV 106 and the neighboringbase station 108.

On the other hand, the neighboring base station 108 performs uplinkmeasurements to detect uplink interference from the uplink transmissionsfrom the UAV 106. If the uplink signal received at the neighboring basestation 108 is higher than a certain threshold and the neighboring basestation 108 is unable to tolerate such interference, then theneighboring cell 108 could decide to transmit the uplink interferenceindicator via an SIB message. Once the interference from the UAV 106 issufficiently reduced or becomes tolerable at the neighboring basestation 108, the neighboring cell 108 has the option to remove theuplink interference indicator from its SIB messaging.

For the example shown in FIG. 3D, the UAV 106 would only transmit theSounding Reference Signal (SRS), including scheduling assignmentinformation for the UAV 106, if the uplink interference indicator ispresent in one of the SIB messages that the UAV 106 is monitoring, basedon the downlink signal strength threshold. In other examples, the UAV106 would transmit a signal on the PRACH instead of an SRS. Since theuplink resources of the UAV 106 are typically allocatedsemi-persistently, the UAV 106 should also inform the neighboring basestations 108, 114 when the scheduled uplink transmissions are stopped.

As described above, the UAV 106 monitors/reads the SIB messages, and theneighboring base station 108 measures the uplink transmissions beforetransmitting the uplink interference indicator. Both of these tasks areperformed in parallel and can be done as on-going background processes.

In some cases, the neighboring cell 108 already has a heavy traffic loadwithin its own cell, or the interference may be coming from other UAVs,and as a result, the Interference-over-Thermal (IoT) level has reachedan intolerable level. In these cases, the neighboring cell 108 may nothave to wait for the uplink transmissions from the UAV 106 and cansimply transmit the uplink interference indicator via SIB messaging.

FIG. 3D depicts the messages that are exchanged between the UAV 106 andthe base stations 102, 108 so that the UAV 106 can select which SystemInformation Block (SIB) messages to monitor based on the signal strengthof downlink signals received at the UAV 106 from the neighboring cells108, 114.

The neighboring base station 108 transmits, via its transmitter 206 andantenna 210, downlink signals to the UAV 106. The UAV 106 receives thedownlink signals with antenna 212 and receiver 214. The downlink signalsare represented in FIG. 3D by signal 330.

Upon receipt of the downlink signals 330, the controller 216 of the UAV106 measures the signal strength of the received downlink signals 330.In some examples, signal strength is an RSRP value. However, any othersuitable signal strength/signal power values can be used. If the signalstrength of the downlink signals 330 received at the UAV 106 from theneighboring cell 108 exceeds a signal strength/signal power threshold,the UAV 106 will begin monitoring System Information Block (SIB)messaging from the neighboring cell 108 that transmitted the downlinksignals 330.

While the UAV 106 monitors the SIB messaging from the neighboring cell108, the neighboring cell 108 will also measure the uplink transmissionsfrom the UAV 106. The uplink transmissions are represented in FIG. 3D bysignal 302. The controller 204 of neighboring base station 108determines whether the uplink transmissions 302 received from the UAV106 are causing a level of interference at the neighboring cell 108 thatexceeds an interference threshold. If the interference caused by theuplink transmissions 302 exceeds the interference threshold, theneighboring base station 108 transmits, via its transmitter 206 andantenna 210, an uplink interference indicator to the UAV 106 in a SIBmessage. The UAV 106 receives the uplink interference indicator withantenna 212 and receiver 214. The signal containing the uplinkinterference indicator is represented in FIG. 3D by signal 304.

Upon receipt of the uplink interference indicator, the UAV 106 transmitsa Sounding Reference Signal (SRS), including the scheduling assignmentinformation for the UAV 106, to the neighboring base station 108 thatsent the uplink interference indicator. The signal containing thescheduling assignment information is represented in FIG. 3D by signal332. As mentioned above, in other examples, the UAV 106 would transmit asignal on the PRACH instead of an SRS.

Upon receipt of the scheduling assignment information, the neighboringcell 108 takes steps to mitigate the uplink interference from the UAV106, such as beam steering or rescheduling uplink transmissions fromother UE devices and/or UAVs being served by neighboring base station108, based on the scheduling assignment information received from theUAV 106. Meanwhile, UAV 106 continues to transmit its uplinktransmissions to the serving cell 102. These uplink transmissions arerepresented in FIG. 3D by signal 334.

FIG. 4A is a flowchart of an example of a method in which a serving cell102 makes a handover decision for the UAV 106 in response to the UAV 106causing excessive uplink interference at a neighboring cell 108. Thesteps of method 400 may be performed in a different order than describedherein and shown in the example of FIG. 4A. Furthermore, in someexamples, one or more of the steps may be omitted. Moreover, in otherexamples, one or more additional steps may be added. In some cases,multiple steps may be performed in parallel.

In the example shown in FIG. 4A, the method 400 begins at step 402, inwhich it is determined that uplink interference from UAV 106 exceeds aninterference threshold at a neighboring cell 108. At step 404, theneighboring base station 108 transmits an uplink interference indicatorto the UAV 106. At step 406, the UAV 106 informs the serving cell 102 ofthe uplink interference experienced by neighboring cell 108. In somecases, the UAV 106 transmits a neighboring cell identifier associatedwith the neighboring cell 108 to the serving cell 102.

At step 408, the UAV 106 transmits a downlink measurement reportassociated with the neighboring cell 108 to the serving cell 102. Theserving cell 102 uses the information received from the UAV 106 to makea handover decision on behalf of the UAV 106. At step 410, the servingcell 102 transmits a handover command instructing the UAV 106 to performa handover procedure to the neighboring cell 108.

FIG. 4B is a flowchart of an example of a method in which a serving cell102 makes a scheduling decision for the UAV 106 in response to the UAV106 causing excessive uplink interference at a neighboring cell 108. Thesteps of method 420 may be performed in a different order than describedherein and shown in the example of FIG. 4B. Furthermore, in someexamples, one or more of the steps may be omitted. Moreover, in otherexamples, one or more additional steps may be added. In some cases,multiple steps may be performed in parallel.

In the example shown in FIG. 4B, the method 420 begins at step 402, inwhich it is determined that uplink interference from UAV 106 exceeds aninterference threshold at a neighboring cell 108. At step 404, theneighboring base station 108 transmits an uplink interference indicatorto the UAV 106. At step 406, the UAV 106 informs the serving cell 102 ofthe uplink interference experienced by neighboring cell 108. At step412, the serving cell 102 allocates a different uplink radio resource tothe UAV 106 to use for uplink data transmissions.

FIG. 4C is a flowchart of an example of a method in which a UAV 106stops using a secondary radio resource in response to causing excessiveuplink interference at a neighboring cell 108. The steps of method 430may be performed in a different order than described herein and shown inthe example of FIG. 4C. Furthermore, in some examples, one or more ofthe steps may be omitted. Moreover, in other examples, one or moreadditional steps may be added. In some cases, multiple steps may beperformed in parallel.

In the example shown in FIG. 4C, the method 430 begins at step 402, inwhich it is determined that uplink interference from UAV 106 exceeds aninterference threshold at a neighboring cell 108. At step 404, theneighboring base station 108 transmits an uplink interference indicatorto the UAV 106. At step 414, the UAV 106 refrains from transmitting onthe uplink resource on which the UAV 106 was transmitting that causedthe uplink interference experienced by neighboring cell 108. In somecases, the UAV 106 stops transmitting on a secondary radio resource.After a period of time, which may be indicated by the expiration of atimer, the UAV 106 resumes uplink transmissions, at step 416. In somecases, the UAV 106 resumes uplink data transmissions using a differentuplink resource than the uplink resource that was being used when theneighboring cell 108 experienced excessive uplink interference.

FIG. 4D is a flowchart of an example of a method in which a UAV 106selects which System Information Block (SIB) messages to monitor basedon the signal strength of downlink signals received at the UAV 106 fromthe neighboring cells 108, 114. The steps of method 440 may be performedin a different order than described herein and shown in the example ofFIG. 4D. Furthermore, in some examples, one or more of the steps may beomitted. Moreover, in other examples, one or more additional steps maybe added. In some cases, multiple steps may be performed in parallel.

In the example shown in FIG. 4D, the method 440 begins at step 418 withUAV 106 monitoring SIB messages from one or more neighboring cells 108,114 whose downlink signals exceed a received signal strength/signalpower threshold measured at the UAV 106. At step 402, it is determinedthat uplink interference from UAV 106 exceeds an interference thresholdat a neighboring cell 108. At step 404, the neighboring base station 108transmits an uplink interference indicator to the UAV 106. In somecases, the UAV 106 transmits its scheduling assignment information in anSRS signal to the neighboring cell 108 that transmitted the uplinkinterference indicator so the neighboring cell 108 can mitigate theuplink interference.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. The above description is illustrative and not restrictive.This invention is to be limited only by the following claims, whichinclude all such embodiments and modifications when viewed inconjunction with the above specification and accompanying drawings. Thescope of the invention should, therefore, be determined not withreference to the above description, but instead should be determinedwith reference to the appended claims along with their full scope ofequivalents.

1. A method comprising: informing a serving cell of uplink interferenceexperienced by a neighboring cell; in response to an unmanned aerialvehicle (UAV) detecting the uplink interference with the neighboringcell, transmitting a downlink measurement report to the serving cell,the downlink measurement report associated with downlink transmissionsreceived by the UAV from the neighboring cell, the downlink measurementreport including an identifier of the neighboring cell.
 2. The method ofclaim 1, wherein informing the serving cell of the uplink interferenceexperienced by the neighboring cell comprises: transmitting an uplinkinterference indicator to the serving cell.
 3. The method of claim 1,further comprising: transmitting a handover command to the UAV.
 4. Themethod of claim 3, wherein the handover command is based on: theidentifier of the neighboring cell that experienced the uplinkinterference, and a downlink measurement report received from the UAV.5. The method of claim 1, further comprising: allocating a differentuplink radio resource to the UAV.
 6. A wireless communication device(WCD) capable of flight without having a human pilot aboard, thewireless communication device comprising a transmitter configured to:inform a serving cell of uplink interference experienced by aneighboring cell; and in response to detecting the uplink interferencewith the neighboring cell, transmit a downlink measurement report to theserving cell, the downlink measurement report associated with downlinktransmissions received by the UAV from the neighboring cell, thedownlink measurement report including an identifier of the neighboringcell.
 7. An apparatus for controlling a wireless communication device(WCD) capable of flight without having a human pilot aboard, theapparatus configured to perform processing of: informing a serving cellof uplink interference experienced by a neighboring cell; and inresponse to detecting the uplink interference with the neighboring cell,transmitting a downlink measurement report to the serving cell, thedownlink measurement report associated with downlink transmissionsreceived by the UAV from the neighboring cell, the downlink measurementreport including an identifier of the neighboring cell.